Regulation of Acanthamoeba castellanii alternative oxidase activity by mutual exclusion of purine nucleotides; ATP's inhibitory effect
| Autor: | Francis Sluse, Wieslawa Jarmuszkiewicz, Andrzej Woyda-Ploszczyca |
|---|---|
| Rok vydání: | 2009 |
| Předmět: |
Purine
Alternative oxidase Guanine Cell Respiration Allosteric regulation Guanosine Monophosphate Biophysics Biology Models Biological Biochemistry Substrate Specificity Mitochondrial Proteins chemistry.chemical_compound Adenosine Triphosphate Allosteric Regulation Adenine nucleotide Animals Dictyostelium Nucleotide Phosphorylation Candida Plant Proteins chemistry.chemical_classification Acanthamoeba castellanii Cyanides Purine nucleotides Alternative oxidase activity Cell Biology Mitochondria Kinetics Solubility chemistry Mutual exclusion Oxidoreductases Nucleoside |
| Zdroj: | Biochimica et Biophysica Acta (BBA) - Bioenergetics. 1787(4):264-271 |
| ISSN: | 0005-2728 |
| DOI: | 10.1016/j.bbabio.2009.01.017 |
| Popis: | The effects of different adenine and guanine nucleotides on the cyanide-resistant respiration (i.e. alternative oxidase (AcAOX) activity) of mitochondria from the amoeba A. castellanii mitochondria were studied. We found that guanine nucleotides activate AcAOX to a greater degree than adenine nucleotides, and that nucleoside monophosphates were more efficient activators than nucleoside di- or triphosphates. The extent of the nucleotides' influence on AcAOX was dependent on the medium's pH and was more pronounced at pH 6.8, which is optimal for AcAOX activity. In contrast to other purine nucleosides, we demonstrate, for the first time, that ATP has an inhibitory effect on AcAOX activity. Since we also observed the inhibition by ATP in the mitochondria of another protozoon, such as Dictyostelium discoideum, and the yeast, Candida maltosa, it may be a regulatory feature common to all purine nucleotide-modulated non-plant AOXs. The physiological importance of this discovery is discussed. Kinetic data show that the binding of GMP (a positive allosteric effector) and the binding of ATP (a negative allosteric effector) to AcAOX are mutually exclusive. ATP's inhibition of the enzyme can be overcome by sufficiently high concentrations of GMP, and conversely, GMP's stimulation can be overcome by sufficiently high concentrations of ATP. However, an approximately three times lower concentration of GMP compared to ATP gives a half maximal effect on AcAOX activity. This is indicative of a higher binding affinity for the positive effector at the same or, at least overlapping, nucleotide-binding sites on AcAOX. These results suggest that AcAOX activity in A. castellanii mitochondria might be controlled by the relative intracellular concentrations of purine nucleotides. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect